Display device utilizing gas discharge

ABSTRACT

The present invention relates to a plasma display panel comprising two substrates defining a gap in which an ionizable gas is disposed. On at least one of the substrates there are a plurality of electrodes disposed on the side thereof closer to said gap. Covering said electrodes are dielectric means which contact said gap. The dielectric means comprises a first portion having a high secondary electron emissivity and a second portion having a secondary electron emissivity lower than said first portion. The plasma display panel according to the present invention can be used to improve the definition of a displayed pattern in the plasma display panel, or as a self shift plasma display panel, and or as a pattern generator in an information processing system.

Shirouchi et a1.

[ DISPLAY DEVICE UTILIZING GAS DISCHARGE [75] Inventors: Yasunari Shirouchi, Akashi;

Toshinori Urade, Kobe, both of Japan [73] Assignee: Fujitsu Limited, Kanagawa-ken,

Japan [22] Filed: Dec. 14, 1972 [21] Appl. No.: 315,017

[30] Foreign Application Priority Data Dec. 29, 1971 Japan 46-751 [52] US. Cl. 313/188, 313/220 [51] Int. Cl. H0lj 61/00 [58] Field of Search 313/l03,l88,220 [56] References Cited UNITED STATES PATENTS 10/1971 Baker et al. 313/188 June 18, 1974 Primary Examiner-Herman Karl Saalbach Assistant ExaminerDarwin R. Hostetter Attorney, Agent, or Firm-Maleson, Kimmelman &

Ratner 5 7] ABSTRACT The present invention relates to a plasma display panel comprising two substrates defining a gap in which an ionizable gas is disposed. On at least one of the substrates there are a plurality of electrodes disposed on the side thereof closer to said gap. Covering said electrodes are dielectric means which contact said gap. The dielectric means comprises a first portion having a high secondary electron emissivity and a second portion having a secondary electron emissivity lower than said first portion. The plasma display panel according to the present invention can be used to improve the definition of a displayed pattern in the plasma display panel, or as a self shift plasma display panel, and or as a pattern generator in an information processing system.

8 Claims, 12 Drawing Figures PAIEMTED JUN I 81974 SHEET 10F PATENTEB JUN? 81974 WEE? E 0? 4 Q' PRIOR ART 1 DISPLAY DEVICE UTILIZING GAS DISCHARGE DETAILED EXPLANATION OF THE INVENTION The present invention relates to an improvement of the display device utilizing gas discharge, especially to a novel display device which utilizes gas discharge dielectric walls contacting a gap filled with gas capable of ionization and is partially composed of two kinds of dielectric materials having respectively different secondary electron emissivity.

Generally, in a display device utilizing gaseous discharge, electrodes covered with dielectric layers are positioned to face each other. Between them, is a gap filled with gas capable of ionization. An alternating sustaining voltage is applied between the electrodes facing each other, and the discharge spots are produced when a writing voltage larger than the firing voltage is added to the sustaining voltage. When the discharge spots are produced, charges corresponding to the polarity of the applied voltage are formed. When the potential difference between the wall voltage due to the wall charges and the following sustaining voltage becomes larger than the firing voltage, the discharge spot is again produced, and the polarity of the wall voltage is reversed. Accordingly, once the discharge is produced, a sustaining voltage lower than the firing voltage can continuously produce the discharge spot. That is, the written information is memorized in the form of a wall voltage and the display can be carried out. Such a gaseous discharge panel has become known in the art as the plasma panel, and when it is utilized for display purposes, it is commonly called the plasma display panel.

On the other hand, a display device capable of self shifting discharge spots is proposed as a modification of the display device utilizing gas discharge. Such a device is one of the plasma display panels and can shift the information of a discharge spot generated in the gap filled with gas capable of ionization by using the primary current effect. The primary current effect is a phenomenon wherein the firing voltage for an adjacent point to the discharge point is decreased due to the emission of electrons, ions and metastable atoms produced by discharge. By the primary current effect, the discharge spot can be shifted in a predetermined direction by applying in order a polyphase voltage to the electrodes.

For carrying out the above-mentioned shift action in each column respectively, it is required that each column be mechanically or electrically separated in the direction of the shift. To achieve this purpose, it has been proposed that mechanical insulation barriers be provided between each column. However, mechanical barriers not only make the structure itself complicated, but also make the assembly work very complex. Further, the space between the columns becomes inevitably large and consequently, the displayed figure be The object of the present invention is to improve the above-mentioned drawbacks of the plasma display panel of the prior art.

Another object of the present invention is to provide a plasma display panel capable of self shifting the discharge spot by providing electrical barriers on the surface of the dielectric layer.

A further object of the present invention is to provide a plasma display panel which can produce figures defined by small, fine spots by providing electrical barriers on the surface of the dielectric layer.

Still another object of the present invention is to provide a plasma display panel which can be used as a pattern generator, utilizing the difference between firing voltages, by providing electrical barriers on the surface of the dielectric layer.

In the present invention, the surface of the dielectric layer covering the electrodes, which face each other with a gap therebetween filled with gas capable of ionization, is partially composed of two dielectric portions. The surface of one of the dielectric portions has a large secondary electron emissivity and that of the other dielectric portion has a small secondary electron emissivity. In the device capable of self shifting the discharge spot, the above difference in secondary electron emissivities is utilized to separate each column and in the usual matrix type display device, to restrict the position of the discharge spot.

The present invention is especially effective in the display device utilizing gas discharge and having a function of self shifting discharge spots. However, as mentioned above it is also effective in the usual matrix type display device utilizing gas discharge.

Further features and advantage of the present invention will be apparent from the ensuing description with reference to the accompanying drawings to which, of course, the scope of the invention is in no way limited.

FIG. 1 is a general view of the typical plasma display panel;

FIG. 2 is a sectional view of the plasma display panel shown in FIG. 1;

FIG. 3 is a plan view of the conventional plasma display panel capable of self shifting the discharge spot;

FIG. 4 is a plan view of one embodiment of the plasma display panel capable of self shifting the dis charge spot according to the present invention;

FIGS. 5A and 5B are two examples of sectional views along AA of the plasma display shown in FIG. 4;

FIGS. 6A and 6B are sectional and plan views of another embodiment of the plasma display panel according to the present invention;

FIG. 7 is a further embodiment of the plasma display panel according to the present invention;

FIG. 8 is still another embodiment of the plasma display panel according to the present invention;

FIGS. 9A and 9B are plan views of still another embodiment of the plasma display panel according to the present invention.

Referring to FIG. 1, a display device utilizing a gaseous discharge 1 has a pair of substrates 2 and 2a supporting electrodes. The supporting substrate 2 provides a group of electrodes 3 arranged in columns, which are parallel to a vertical axis and are covered by a dielectric layer 4. The supporting substrate 2a provides a group of electrodes 3a arranged in rows, which are parallel to a horizontal axis and are covered by a dielectric layer 4a. The supporting substrates of electrodes 2 and 2a are positioned in spaced parallel relation so that the groups of electrodes 3 and 3a are disposed at right angles to each other. As shown in FIG. 2 these parallel rows and columns are separated from each other by a gap 5. This gap is filled with a rare gas having a suitable pressure and being capable of ionization. When the device is utilized for display purposes, it is necessary that at least one of the substrates 2, 2a and one of the dielectric layers 4, 4a are transparent.

In the above-mentioned display device utilizing gas discharge 1 shown in FIGS. 1 and 2, when an electric voltage higher than the firing voltage V; is selectively applied between the groups of electrodes in columns 3 and rows 3a, each cross point of the electrodes in columns and rows discharges into the gap 5 filled with ionizable gas. At the time of this discharge, a wall charge is formed on the surfaces of the dielectric layers 4 and 4a corresponding to the above-mentioned cross point. With the effect of this wall charge, the discharge, once generated, is sustained with the pulsive sustaining voltage V, smaller then the firing voltage V;. That is, the input information which is the voltage exceeding the firing voltage V, is memorized by the above-mentioned wall charge.

Referring to FIG. 3, this device provides a plurality of shift electrodes 12, 13, 14, 15, etc. arranged parallel and connected at intervals of two electrodes to a common buss of a three phase alternating current electric source. Also, a plurality of write electrodes 11 is arranged in every column longitudinally along the first shift electrode 12. These electrodes 11, 12, l3, 14, 15, etc., are covered with a dielectric layer and face a gap filled with gas capable of ionization.

When the firing voltage is supplied between the write electrode 1 l and the first shift electrode 12, a discharge spot 17'is produced between these two electrodes. In this case, when the three phase sustaining voltage is commutated to shift electrodes 12, 13, 14, etc., in order, the above-mentioned discharge spot is shifted in order, in a direction at right angles to the shift electrodes. However, to carry out the above-mentioned shift action, it is required that each column be mechanically or electrically separated in the direction of the shift. To achieve this purpose, it has been proposed that mechanical insulation barriers 16 be provided between each column for the purpose of preventing the deviation of the discharge spot as shown in the deviation 19. However, the mechanical barriers 16 not only make the structure complex, but also complicate assembly work. Further, the spaces between columns become inevitably large and the displayed figure becomes unsightly. It has also been proposed that other electrodes be provided in the center of each column or between each column and these electrodes be supplied by the voltage to separate electrically the mutual effect between the columns. However, reliable functioning cannot be anticipated with this method.

The preferable embodiment according to the present invention will now be explained with respect to FIGS. 4-9. FIGS. 4, 5A and 5B are one example of the present invention applied to the device capable of self shifting discharge spots. The electrodes 12, 13, 14, 15, etc., shown in FIG. 4 are formed parallel to the common plane of the base plate 24 which is shown in the sectional view of FIG. 5A. As in FIG. 5A, the wall surface,

which is composed .of two portions 20 and 21, covers the above-mentioned electrodes and faces another base plate 22 and gap 23 between them is filled with gas capable of ionization. The dielectric wall surface 21, which contacts the gap 23 at positions corresponding to each column, can be constructed with material having high secondary electron emissivity y for example, low melting temperature glass which includes more than per cent PbO. The dielectric wall surface 20, which contacts the gap 23 between each column, can be constructed with material having a lower secondary electron emissivity 1 than that of material 2i, for example, Al O SiO Referring to FIG. 5A, the dielectric wall surfaces 20, which separate each column, are disposed on the dielectric wall surface 21, which has high secondary electron emissivity 14;. Referring to FIG. SB, the dielectric wall surfaces 20, having low secondary electron emissivity 71,, are buried between each column in the dielectric wall surface 21, having high secondary electron emissivity y in such a manner that the surfaces of 20 and 21 facing the gap 23 have the same surface plane.

As a result of this, a difference of the firing voltages in a ratio of about 1 2 is produced between the dielectric wall surface 21, composed of low melting temperature glass including H20, and the dielectric wall surface 20, composed of high melting temperature glass including Al O due to the difference in secondary electron emissivity. This difference of firing voltages between the dielectric wall surfaces 20 and 21 can be increased to a ratio of about 1 5 by chemically treating with cesium C or a compound of cesium C the dielectric material having a high secondary electron emissivity 7/ Furthermore, this difference in the secondary electron emissivity can also be provided by selectively treating the dielectric surface by means of etching with acid or alkaline solvent. Then, when the voltage applied to the shift electrodes l2, l3, 14, etc., is previously selected below the firing voltage of the dielectric wall surface 20, having a low secondary electron emissivity n, the discharge spots of each column can be prevented from moving to an adjacent column.

FIGS. 6A and 63 represent another embodiment of the present invention applied to the device capable of self shifting the discharge spot. Referring to the sectional view shown in FIG. 6A, a plurality of electrodes 25 disposed in parallel on the base plate 22 are covered with a first dielectric layer 26. As is clear from the plan view of FIG. 68, second dielectric layers 27 are provided at right angles to the electrodes 25 on the surface of the first dielectric layer 26. On the other hand, a plurality of electrodes 25a, disposed parallel to the base plate 24 are covered with a first dielectric layer 260. The second dielectric layers 27a disposed parallel to and between the electrodes 25a are provided on the surface of the first dielectric layer 260. As already shown, the group of electrodes 25 and that of electrodes 25a are disposed at right angles to each other and the second dielectric layers 27 and 270 are disposed parallel to and facing each other with the gap 23 filled with ionizable gas therebetween. The first dielectric layers 26, 26a and the second dielectric layers 27, 27a are respectively composed of dielectric materials having different secondary electron emissivity y. For example, the first dielectric layers 26, 26a can be composed of low melting temperature glass which includes more than 70 percent PbO, and the second dielectric layers 27, 27a can be composed of AI O or SiO The plasma display panel shown in FIGS. 6A and 68 provides electric barriers 26, 26a, 27 and 27a disposed parallel to the electrodes 25a. Consequently, when the polyphase voltage is supplied to the electrodes 25, the discharge spot 19 can be shifted along the passages be tween said electric barriers.

FIG; 7 is a sectional view of a further embodiment of the present invention applied to a matrix type display device utilizing gas discharge. Referring to FIG. 7, X electrodes and Y electrodes 15a, disposed respectively on a pair of base plates 22 and 22a, are covered with dielectric layers 21 and 21a having high secondary electron emissivity 7 These base plates 22 and 22a are disposed in spaced parallel relation facing each other with a gap 23 filled with gas capable of ionization therebetween. Further, in the display device shown in FIG. 7, dielectric layers 20, having low secondary electron emissivity n, are provided upon the dielectric layer 21, having high secondary electron emissivity 7,, in positions which correspond to the intervals between the Y electrodes 15a. Similarly, dielectric layers a, having low secondary electron emissivity 'y are pro vided upon the dielectric layers 210, having high secondary electron emissivity 7 inpositions which correspond to the intervals between the X electrodes 15. Accordingly, the cross points of X electrodes 15 and Y electrodes 15a correspond to meshes of the dielectric layers 20 and 20a which are disposed in lattice form each other. According to the construction shown in FIG. 7, the cross points of X electrodes 15 and Y electrodes 15a are exposed to portions of the dielectric layers 21 and 21a which have high secondary electron emissivity y The firing voltages at these cross points are low, and, consequently, the dimensions of the discharge spots generated at these cross points are restricted. That is, the discharge spot is prevented from enlarging unnecessarily and incorrectly moving to the adjacent position to be discharged, as is seen frequently in the conventional display device.

FIG. 8 is a sectional view of still another embodiment of the present invention applied to a display device utilizing gas discharge. In FIG. 8, contrary to that shown in FIG. 7, X electrodes 15 and Y electrodes 15a, disposed respectively on a pair of base plates 22 and 22a, are covered with dielectric layers 24 and 24a respectively, which have low secondary electron emissivity. Dielectric layers 25 and 25a, having high secondary electron emissivity, are disposed on the surface of the dielectric layers 24 and 24a, and face each other with the gap 23 filled with ionizable gas therebetween, to cover the cross points of the electrodes X and Y. In the construction shown in FIG. 8 the cross points of X electrodes 15 and Y electrodes 150 are also exposed to a portion of the dielectric of the layers 25 and 25a, which have high secondary electron emissivity 'y. The firing voltages at these cross points are low and consequently, the dimensions of the discharge spots generated at these cross points are restricted. That is, similar to the case of FIG. 7, the discharge spot is prevented from enlarging unnecessarily and incorrectly moving to an adjacent position, as is seen frequently in the conventional display device.

FIGS. 9A and 9B are an embodiment of the present invention applied to a pattern generator. In the embodiment shown in FIG. 9A, X electrodes 15 and Y electrodes 150 are disposed at right angles to each other in the plasma display panel. The portions of the dielectric layers having high secondary electron emissivity are selectively provided on the selected cross points of the X and Y electrodes, that is, cells 28 having low firing voltage are selectively provided. It is understood that the above-mentioned cells 28 form a pattern in accordance with the desired figure, such as the character A shown in FIG. 9A. In the plasma display panel constructed according to FIG. 7, when the voltage having a suitable value is supplied to the cross points of whole electrodes, the selected cells 28 having low firing voltage, that is, only the cells forming the desired pattern, can fire selectively. Consequently, the electric signal corresponding to the pattern can be obtained by reading electrically the state of each cell. As shown in FIG. 9B, the same effect can be obtained by the negative pattern 29 having low secondary electron emissivity disposed on the surface of a dielectric layer having high secondary electron emissivity and making the high firing voltage correspond to the portion of the negative pattern.

What is claimed is:

l. A display device utilizing gas discharge which is composed of:

a. a pair of substrates which are facing each other so as to define a discharge gap which is filled with a gas capable of ionization,

b. a plurality of electrodes which are disposed on at least one of said substrates on the side thereof closer to said gap, and

c. dielectric means covering said electrodes and contacting said discharge gap, said dielectric means comprising a first portion which has a high secondary electron emissivity in accordance with a predetermined configuration and a second portion which has a secondary electron emissivity lower than that of said first portion.

2. A display device according to claim I wherein said plurality of electrodes are disposed in parallel, wherein said second dielectric portion comprises a layer covering said electrodes, and wherein said first dielectric portion comprises a plurality of strips disposed in contact with said dielectric layer and facing said gap.

3. The display device according to claim 2 with the addition of means for applying a polyphase voltage to said electrodes thereby shifting discharge spots generated between adjacent electrodes along said strips.

4. The display device according to claim 1 wherein said plurality of electrodes includes a first and second set of electrodes arranged at right angles to each other and are respectively covered by said dielectric means, said sets being positioned in spaced parallel relation facing one another with said discharge gap therebetween, the first portions of said dielectric means comprising a plurality of parallel dielectric strips having a higher secondary electron emissivity than that of said dielectric means, said strips corresponding to said first set of electrodes and means for applying a polyphase voltage to said second set of electrodes, said voltage applying means being connected to said second set of electrodes and being disposed at right angles to said strips, said applying means producing discharge spots at cross points between said first and second set of electrodes which are shifted along said strips by said applied voltage.

5. The display device according to claim 1 wherein said plurality of electrodes includes first and second sets of electrodes arranged at right angles to one another, wherein said dielectric means comprises first and second dielectric layers respectively covering said first and second sets of electrodes, said dielectric layers being positioned and spaced in parallel relation with their surfaces facing each other across said discharge gap, wherein the respective second portions of said layers comprise a plurality of dielectric strips arranged at right angles to one another.

6. A display device according to claim 1 wherein said plurality of electrodes includes first and second sets of electrodes arranged at right angles to one another and wherein said dielectric means includes first and second dielectric layers respectively covering said first and second sets, said dielectric layers being positioned and spaced in parallel relation on each side of said discharge gap, wherein the first portions of said two dielectric layers comprise first and second pluralities of dielectric strips.

7. The gas discharge device according to claim 1 wherein said plurality of electrodes comprises first and second sets of electrodes, wherein said dielectric means comprises first and second dielectric layers covering said first and second electrodes, said dielectric layers being spaced from one another with said discharge gap between, the first portion of at least one of said layers being covered with a predetermined configuration of a dielectric material having a higher secondary electron emissivity than that of said dielectric layer.

8. The gas discharge device according to claim 1 wherein said plurality of electrodes comprises two sets of electrodes, wherein said dielectric means comprises two dielectric layers respectively covering said sets of electrodes, said dielectric layers being spaced from one another with said discharge gap between them, and wherein the second portion of at least one of the said layers is covered with a pattern of dielectric material having lower secondary electron emissivity than that of said one of said layers.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION- PATENT N0. 3 1 25 DATED June 18, 1974 INVENTOR( I YASUNARI SHIROUCHI et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 8, delete "covered with";

line 10, before "said" insert said second portion line 18, delete "covered with";

line 20, before first occurrence of "said" insert --said first portion of--.

Signed and Scaled this First Day of August 1978 [SEAL] Attest:

DONALD W. BANNER RUTH C. MASON Attesting Officer Commissioner of Patents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,818,258 Dated June 48, 1974 Inventor(s) YASUNARI SHIROUCHI et al It is certified that error appears in the above-identified 'patent and that said Letters Patent are hereby corrected as shown below:

Column 8, line 7, delete "at least one of";

line 8, delete "covered with";

. line 10, after "said" insertsecond portion of said line 17, delete "at least one of the";

line 18, after "is" insert-a predetermined configuration;

line 18, delete "covered with a pattern";

line 20, delete "one";

. line 20, before "of" insert-first portion.

gigncd and Sealed this Thirtieth D of Q gsrpxu RL'IH MASON LU'lRl-ILLF. F. PARKER Am'uing ()jliu'r Acting Commissioner of Parents and Trademarks Notice of Adverse Decision in Interference In Interference No. 99,541, involving Patent No. 3,818,258, Y. Shirouchi and T. Urade, DISPLAY DEVICE UTILIZING GAS DISCHARGE, final judgment adverse to the patentees was rendered Oct. 21, 1983, as to claims 2 and 6. Y

[Ofiicial Gazette June 5, 1984.] 

1. A display device utilizing gas discharge which is composed of: a. a pair of substrates which are facing each other so as to define a discharge gap which is filled with a gas capable of ionization, b. a plurality of electrodes which are disposed on at least one of said substrates on the side thereof closer to said gap, and c. dielectric means covering said electrodes and contacting said discharge gap, said dielectric means comprising a first portion which has a high secondary electron emissivity in accordance with a predetermined configuration and a second portion which has a secondary electron emissivity lower than that of said first portion.
 2. A display device according to claim 1 wherein said plurality of electrodes are disposed in parallel, wherein said second dielectric portion comprises a layer covering said electrodes, and wherein said first dielectric portion comprises a plurality of strips disposed in contact with said dielectric layer and facing said gap.
 3. The display device according to claim 2 with the addition of means for applying a polyphase voltage to said electrodes thereby shifting discharge spots generated between adjacent electrodes along said strips.
 4. The display device according to claim 1 wherein said plurality of electrodes includes a first and second set of electrodes arranged at right angles to each other and are respectively covered by said dielectric means, said sets being positioned in spaced parallel relation facing one another with said discharge gap therebetween, the first portions of said dielectric means comprising a plurality of parallel dielectric strips having a higher secondary electron emissivity than that of said dielectric means, said strips corresponding to said first set of electrodes and means for applying a polyphase voltage to said second set of electrodes, said voltage applying means being connected to said second set of electrodes and being disposed at right angles to said strips, said applying means producing discharge spots at cross points between said first and second set of electrodes which are shifted along said strips by said applied voltage.
 5. The display device according to claim 1 wherein said plurality of electrodes includes first and second sets of electrodes arranged at right angles to one another, wherein said dielectric means comprises first and second dielectric layers respectively covering said first and second sets of electrodes, said dielectric layers being positioned and spaced in parallel relation with their surfaces facing each other across said discharge gap, wherein the respective second portions of said layers comprise a plurality of dielectric strips arranged at right angles to one another.
 6. A display device according to claim 1 wherein said plurality of electrodes includes first and second sets of electrodes arranged at right angles to one another and wherein said dielectric means includes first and second dielectric layers respectively covering said first and second sets, said dielectric layers being positioned and spaced in parallel relation on each side of said discharge gap, wherein the first portions of said two dielectric layers comprise first and second pluralities of dielectric strips.
 7. The gas discharge device according to claim 1 wherein said plurality of electrodes comprises first and second sets of electrodes, wherein said dielectric means comprises first and second dielectric layers covering said first and second electrodes, said dielectric layers being spaced from one another with said discharge gap between, the first portion of at least one of said layers being covered with a predetermined configuration of a dielectric material having a higher secondary electron emissivity than that of said dielectric layer.
 8. The gas discharge device according to claim 1 wherein said plurality of electrodes comprises two sets of electrodes, wherein said dielectric means comprises two dielectric layers respectively covering said sets of electrodes, said dielectric layers being spaced from one another with said discharge gap between them, and wherein the second portion of at least one of the said layers is covered with a pattern of dielectric material having lower secondary electron emissivity than that of said one of said layers. 